[docs] [issue17040] Document context manager support for shelf objects

[Roundup Robot]

Roundup Robot added the comment:

New changeset 935a286b8066 by Ezio Melotti in branch 'default':
#17040: document that shelve.open() and the Shelf object can be used as context managers.  Initial patch by Berker Peksag.
http://hg.python.org/cpython/rev/935a286b8066

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nosy: +python-dev

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